Process for the selective hydrogenation of arylnitroolefins and products thereof



Patented Sept. 27, 1949 UNITED sTATEs enser QEFICETY PROCESS Eon THE SELECTIVE HYDRO- GENATION OF'ARYLNITROOLEFINS AND PRODUCTS THEREOF Charles D. Hurd, Evanston, Ill., assignor to Commercial Solvents Corporation, Terre Haute,

Ind., a corporation of Maryland No Drawing- Application June 20, 1945, Serial No. 600,654

past to form aryloxoalkane oximes, mixtures of aryloxoalkanes and arylami'noalkanes or mixtures of all three of these compounds. v

In the prior processes described above, it was the ultimate objective to obtain the arylaminoalkanes. This was accomplished in the case of the oxime by'reduction in alcoholic oxalic acid solution in the presence of a platinum catalyst. But yields were low, and the process was so expensive as to be un'satisfactory. In the cases where mixtures of oxime and ketone or aldehyde are to be further reduced to the amine, there is a tendency for the amines andketones to combine making ultimate separation dimcult. This is likewise the case where amines and carbonyl compounds are formed together inthe initial reduction process; I

Certain other investigators have attempted to produce the 1-aryl-2-nitroalkanes by the hydrogenation of the-1-aryl-2-nitro-1-alkenes but have been unsuccessful in isolatinglany of the 1-aryl-2- 1 nitroalkane.

' I have now found that l-aryl- 2-nitro-l alkenes can be selectively hydrogenated to produce substantial yields of 1-aryl-2-nitroalkanes, virtually free of amines, together with quantities of 1-aryl- 2-oxoalkane oximes and l-aryl-Z-oxoalkanes. By my process, catalytic reduction of the l-aryl-Z- nitroalkene is carried out under controlled, neutral, low temperature conditions in the presence of a platinum or a palladium catalyst.

The 1-ary1-2-nitroalkanes obtained in accordance with my invention may be used directlyin the preparation of 1-aryl-2-aminoalkanes by reduction of the nitro group or they may be converted to the corresponding l-aryl-Z-oxoalkane as describedin copending application of John B. Tindall, Serial No. 600,653, now Patent No. 2,427,- 822, filed as of even date herewith; or they may be used to prepare new nitro alcohols by reac--;

tion with an aldehyde and thesenitro alcohols in turn maybe converted into the corresponding amino alcohols. These compounds have valuable physiological properties, having the structural configuration which imparts; to fbenze-l 5 Claims. (Cl. 2.60566) 2 drine, desoxyephedrine-and the like their physiological eliectiveness.

The 1-aryl-2-nitr0-1-alkenes which serve as starting materials in my process may be illustrated by the following structural formula H No,

' t V V Aryl-C: R wherein R may be an alkyl radical. I 1; Upon hydrogenation, substantial yields of 1- aryI-Z-nitroalkanes are obtained represented by the formula along with usually somewhat lesser quantities of the aryloxoalkanes and aryloxoalkane oximes.

In carrying out my invention, the 1-aryl-2- nitro-l-alkene, together with an inert, neutral solvent and .a small quantity of platinum or palladium catalyst is placed in a pressure vessel. The vessel is closed, heated and hydrogen is passed intothe vessel under pressure until hy drogen absorption appears substantially to cease. The hydrogenation products are then separated from the catalyst and the inert solvent is removed. The hydrogenation. products may then be separated if desired by suitable means as by 30 fractionation.

As a liquid reaction medium, any suitable inert, neutral solvent may be used such as water, alcohols, ketones, benzene, toluene and the like.

The temperature of hydrogenation should be as low as is consistent with adequate hydrogen absorption as higher temperatures appear to promote formation of some quantities of undesired amines which tend not only to lower the yields of 1-a-ryl-2-nitroalkane and the accompanying oxime and carbonyl compounds, but also to combine with them in such a way as'to make separation by fractionation difiicult. A temperature of at least about 15 C. is necessary for reasonably rapid hydrogenation, and up to about 40 'C'. may generally be used before the undesired, interfering amine begins to form. I therefore prefer to carry tout my hydrogenation between these two temperature limits of about 15 C. to 40 C. to obtain yields of I-aryI-Z-nitroal- 3.3 a .W. 1 .as overall yields of combined products in the form of arylnitroalkanes, aryloxoalkanes and aryloxoalkane oximes, and temperatures between about 18 and 30 C. are usually preferred.

The hydrogenation is carried out under pressures, and this factor is not particularly critical, pressures between and 500 lbs/sq. inch being suitable and pressures between 200 and 500 lbs/sq. inch being most satisfactory for palladium catalyst while somewhat,lowenpressures in the range between 15.,and 1,00 lbs/sq. inch are most satisfactory for platinum catalyst.

The yields of arylnitroalkanes are substantial, ranging from about to over depending somewhat on the l-aryl-2-nitro+l alkenel.used. as. H]

starting material, and the-solvent-empleyed as a reaction medium. The overall yields of the three products obtained are usually-lhigh, ranging from about '70 to 90%.

The products of my invention may beareco-vered severally in the usual wayjoy fractionation or the like since no interfering amines are present to complicate the recovery.

The following specific examples will-cf-urther illustrate my invention.

EXA'MPIJE I Armi tu-r of :ZO 'YQa-r 0 rnhenyl-z-nitro-lprp e iesfi parsp. -.-;Wat r 1 s $2P fa pa adiumce wh tcea W splace i pressure vessel. The vesselwas closed, and hydrogen was passed in at a temperature between 31 and 35 C. and at 500 lbs. pressure until hydrogen absorption ceased. lTheihydrogern absorption;was1.38 moles-(per; mole. of 1-.phenyl ;2..-pitro;.-lepropene. gThe =vessel .;-.-wasethenlsopened,aandvthe catalyst filtered from the reaction mass. Theresidue consisted of an upper water layer and a lower oil layer. The oil layer amount ed to 180.5 parts and was neutral to methyl red. The water layer was treated with equivalent HCl and 100 parts of water and distilled through a column until free from methanol. The layers in the residue were separated and the oil layer was distilled from a Claisen flask. At 1 mm. pressure 119 parts of distillate was obtained at 86-98 C. This distillate was fractionated through a column at 1 mm., the following fractions being collected.

Parts 1-...70.. ..90f 16.2 2590+i95 71.8 3. 95-110 15.1 .qResidue 3.6

. Fraction. 2, --.consisting of 2-nitro-1- (m-tolyl) rppaneecontained 7.65% N (theo. 7.82%) and ,att 'aarefirantive index n =1.519. The yield of phenylnitroalkane was 40.5%, the total yield of yproducts; 611.8%

:EEXAMPLE III iaAqnixture. ,Dfj142.7 parts of Z-nitro-l-(p-iso- .inropylphenyl) -l-propene, 500 parts of methanol and a parts of 5% palladium on charcoal was hydrogenated at 18-20 C. and at 300 lbs. pressure.

The product was distilled until free from methinganalysis:

Nitrogen, 6.52%...(theo; 6.77%) Refractive. index,-,%2ll'=,l.5l09

d-Jsing.1the:general;prceedure describedvin:rExample.'1;;lephenyle2 nitro -1spropene; lep-henyl- .a2 nitro-liebutene land 3 laphenyl'ezsnitroslapentenezw ere hydrogenated:undentheconditionsand loss-with the results-indicateddmTableI.

IABLE I Reduction .0 mitggoQlciins .1 z lfield gercent l qempf -P1essure, T fl lqq fifi Solvent 0, m z {My} 1 .Ketpn q 1 am; 'l' tikane, 1

"4.9' eao 711.3 3.35.2 7 10.5 5156.2 ..2o.9 82.6 6L8 "43.0 41.0 90.8 20 5.3 30.3 ;:42.0 2.73.1 -.17.3 45,6 ,.1a.2 -76.1 500 9.7 158.2 -11.0 78.9 l vlm n 58.0 29.5 .350 5.12.5 l t n .300 .11.5 40.5 .9.s ,,61.8 w-l-(pp opy p enybextracted with benzene and the benzene and oil N --1, a an .7 V I l ,s 1

layerswere fractionated. I Afterrernoval of'b en- M e.a nd watertlie rollowing fractions were obta e a lmm-rr ss r admi ture. o 1. P i 9 1 i r ml-propeneg fipo parts of methanol and i 3 parts 7 of ..%.l a la .ium ll q kwa h dr nat a q.=lq rdro n nrgssllre an attzoizlt h 60 propenefl lfi parts 'of,. ac,eton e,-and-0:15 part of 2 0 3.0: and at; 45"l b. pressure. -Thenthe-catalyst was filtered oil", 3 the solvent vaporated; and the reaction product distilled. Five :parts '-of 1- yl:2-n itr opropane. was collected at 126-128" 12Qinm,) and an equal weight of 1-phenyl-2-=ni- -tro 1 ;pr opene ljI;' P.; fj3lfwas recovered at 132- fmm-) Th e r en i' 1 phenylnitropropenel based on the consumed-niplatinum pride catalyst hydrogenated -at ;trQolef in.' A"da rkf colored residue remained in phenylnitropropane wassoluble in dilute sodium} lllYdlQXldtfQlllliiOn; and witnnitrous-acid it gaye rise to"thecharacteristimblue colored product from the bomb was "filtered. It was-= pseudo nitrolel TABLE II pene in the liquid phase under neutral conditions at temperatures between about C. and about Properties of arylm'troalkanes Boiling Pr Refractive Specific essure, Nitrogen Nltrogen Compound 3 6? mm. Hg. 23" gf gt d Found Calculated 1-Pheny1-2-nitropropane 78-79 1 1. 520 1. 087 8. 54 8- 50 l-Phenyl-Z-mtrobutane 92-94 1 1. 517 1. 059 7. 98 7- 33 1-Phenyl-2-mtropentane 95-97 1 1. 511 1. 043 7. 28 7. 26 2-Nitr0-1- (m-tolyl) -propane 90-95 1 l. 519 7. 65 7. 82 2-Nlt1'o-1- (p-isopropylphenyD-propanc 99-103 1 1. 5109 1. 025 6. 6. 77

While the above describes the preferred embodiments of my invention, it will be understood that modifications may be made therein and departures therefrom within the scope of the specification and claims.

What is claimed is:

1. A process for the selective hydrogenation of arylnitroolefins of the general formula wherein R is an alkyl group, to obtain a composite reaction product comprising a mixture of 1-aryl-2-nitroalkanes; 1-aryl-2-oxoalkanes and 1-aryl-2-oxoalkane oximes; which comprises subjecting said arylnitroolefin to catalytic hydrogenation, at pressures ranging from 45 to 500 pounds per square inch, in the liquid phase under neutral conditions at temperatures below about 40 C. and in the presence of a noble metal 35 catalyst selected from the group consisting of platinum and palladium.

2. A process for preparing l-aryl-2-nitroalkanes having the following general formula H N 02 Arm-elk C., in the presence of a noble metal catalyst selected from the group consisting of platinum and palladium.

4. In a process for preparing l-phenyl-Z-nitrobutane, the steps which comprise selectively hydrogenating, at pressures rangin from to 500 pounds per square inch, 1-phenyl-2-nitro-1-butene in the liquid phase under neutral conditions at temperatures between about 15 C. and about 40 C., in the presence of a noble metal catalyst selected from the group consisting of platinum and palladium.

5. In a process for preparing 1-phenyl-2-nitropentane, the steps which comprise selectively hydrogenating, at pressures ranging from 45 to 500 pounds per square inch, l-phenyl-Z-nitro-l-pentene in the liquid phase under neutral conditions at temperatures between about 15 C. and about 40 C., in the presence of a noble metal catalyst selected from the group consisting of platinum and palladium.

CHARLES D. HURD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,427,822 Tindall Sept. 23, 1947 FOREIGN PATENTS Number Country Date 406,149 Germany Nov. 14, 1924 571,794 Germany Mar. 15, 1933 629,313 Germany Apr. 30, 1936 OTHER REFERENCES Sonn et al.: Berichte, vol. (1917), page 1515.

Chemical Abstracts, vol. 12, page 40, abstract of article by Asakina.

Hass et al.: Chemical Reviews, vol. 32 (1943), pages 412, 413. 

